Ignition key switch apparatus with improved snap action mechanism

Abstract

An ignition key switch apparatus having a compact size, high current capability, and a snap action mechanism. A pre-loaded snap spring can be configured to include a fixed end attached to an anchor and a free end attached to a movable contact operable between normal and actuated positions. A cam can be utilized to convert a rotary motion at a key interface into a linear movement of a plunger for snap spring blade actuation. The unique pre-loaded snap spring generates a fast (e.g., instantaneous) movement from an open to a closed position and vice versa upon application/removal of a load to reduce the effect of arcing on associated contacts and conductors. The pre-loaded snap spring also ensures that the movable contact does not remain in any intermittent position, other than the two extreme positions given at any position of the plunger.

1. An ignition key switch apparatus with an improved snap action mechanism, comprising:
 a lock cylinder having an opening and to slidably receive a key therein; 
 an anchor disposed within and coupled to the lock cylinder in cantilever fashion, and having a fixed end and a free end, the fixed end coupled to the lock cylinder; 
 a pre-loaded snap spring disposed within the lock cylinder and having a fixed end attached to the fixed end of the anchor, an intermediate portion coupled to the free end of the anchor, and a free end having a movable contact attached thereto, wherein said pre-loaded snap spring generates an instantaneous movement from an open position to a closed position and vice versa upon application or removal of a load to reduce an effect of arcing on a plurality of contacts; 
 a plunger disposed within the lock cylinder and engaging the snap spring, the plunger configured to selectively implement linear movement to a plurality of positions to thereby apply or remove the load to the snap spring, and 
 a cam disposed within said lock cylinder and configured to convert rotary motion at a key interface to the linear movement of said plunger to effectuate the snap spring actuation, 
 wherein said snap spring ensures said movable contact does not remain in any intermittent position other than at least two extreme positions at any position of said plunger. 
 
     
     
       2. The apparatus of  claim 1  wherein said pre-loaded snap spring comprises a snap spring blade with a force balance type snap action mechanism. 
     
     
       3. The apparatus of  claim 1  wherein said pre-loaded snap spring comprises a snap spring blade with an over-center type snap action mechanism. 
     
     
       4. The apparatus of  claim 1  further comprising:
 an actuating lever associated with said plunger and said movable contact and at least two stationary contacts, wherein one of said at least two stationary contacts comprises a normally open contact and another of said at least two stationary contacts comprises a normally closed contact. 
 
     
     
       5. The apparatus of  claim 4  wherein said movable contact and said at least two stationary contacts each comprise a metal for arc quenching. 
     
     
       6. The apparatus of  claim 5  wherein said metal comprises silver tin oxide.